Leak Down Test - How to use this tool?

[mmasse]

I am trying to perform a leak down test on my engine, but I am having trouble understanding how to use this tool.

I followed the instruction that came with it, but something is off.

I connected the compressor to the tool, then the other side to the tool to the cylinder which is at TDC. Then, I turned the regulator counter clockwise iuntil it reads 0, but nothing happens. The needle stays at zero, even thoug I can hear air going out of the cylinder.

I tested on another cylinder and same thing, except on that othe one I can not hear any air going out.

What am I doing wrong?? Please HELP

Thanks

[yelcab1]

You connect the input air hose to the connection on the left.
You connect the long hose on the right to the cylinder under test.
You make sure you have 120 psi on the input
You turn the regulator so that it reads 100 psi, on the left hand side guage
You read the guage on the right side.

If it says 95, you have 5% leak down
If it says 90, you have 10% leak down

[ivangene]

there are 2 TDC's make sure you are on the right one

top of compression stroke not top of exhaust stroke

[mmasse]

Originally Posted by yelcab1

You connect the input air hose to the connection on the left.
You connect the long hose on the right to the cylinder under test.
You make sure you have 120 psi on the input
You turn the regulator so that it reads 100 psi, on the left hand side guage
You read the guage on the right side.

If it says 95, you have 5% leak down
If it says 90, you have 10% leak down

Well, that's the problem. The instructions say to turn the regulator until the right needle reaches the zero mark, but that would show only about 10psi on the right, and the the needle on the right will not move from zero.
If I turn the regulator until it should, let say 80 psi, then the needle on the right goes well pass the zero mark and stays there.

this is driving me crazy!!!

Yes, I have checked that I am at compression TDC. But even if I am not, what I would expect is the tool to give me a high leak reading (close to 100%), right?

[Packet82]

Here's a video of how to do a leakdown test:

How To Perform A Leak Down Test - YouTube

[mmasse]

I watched the video and it seems that the guy on it is also having some difficulty using the leak down tester.

I noticed that he does something different than what is stated on the instructions for the device. He sets the tool to zero before connecting the side that goes to the spark plug hole. Then when he connects to the spark plug hole he gets an immediate drop which he says is the leak percentage.

Does this sounds right to you? The reason I ask is because the guy mentions that even though the tool shows 100% leakage he can not hear the air going anywhere....it really looks that he is as lost as I am!!,

Anyone who has done this before can provide a step by step procedure for this?

Thanks again

[yelcab1]

I have always done it the way I described. Get 100psi in the left side, read the value on the right side and the difference is the leak down percentage.

[Packet82]

Originally Posted by mmasse

I watched the video and it seems that the guy on it is also having some difficulty using the leak down tester.

I noticed that he does something different than what is stated on the instructions for the device. He sets the tool to zero before connecting the side that goes to the spark plug hole. Then when he connects to the spark plug hole he gets an immediate drop which he says is the leak percentage.

Does this sounds right to you? The reason I ask is because the guy mentions that even though the tool shows 100% leakage he can not hear the air going anywhere....it really looks that he is as lost as I am!!,

Anyone who has done this before can provide a step by step procedure for this?

Thanks again

Yeah, he bought the cheap harbor freight one. They don't work particularly well, but the procedure is sound.

The process is pretty simple though. Set it to TDC for that cylinder, set the incoming pressure on the leakdown tester, attach it to the spark plug hole, and then read the difference on the second gauge. The difference will give you your % lost.

Repeat on all the other cylinders. Note that cyl 6 can be a giant pain in the ass to do. I believe pelican sells an adapter that makes it a bit easier to do a leakdown test on a 911 engine, but I haven't used it before.

[kevin-ct]

Is the engine turn a bit when you connect the air supply hose? In the pass when doing a leak down test the engine would turn a bit knocking it off TDC.

As stated, connect the air hose, set the regulator and then hook up the hose that goes into the cylinder.

Do you have a straiter valve in the bottom of the hose that goes into the engine? I think you will need to remove that first.


If you need help, I'm only 30 minuets away..

Kevin
86 911

[T77911S]

the harbour feight one i bought did not go to 100psi on the left. i think it wasa like 15 psi. i too have had problems with it, kinda came up with my own tests with it, more or less to compare cyclinders to each other more than a standard % reading because it dont trust it.

i have some other gauges i am planning on swapping out so i can get the 100psi on the left gauge, just have not done it.

[dad911]

Connect to compressor on left side. Don't connect right side yet, so it is blocked. Adjust for 0% leakdown on right gauge, that will give you a 'benchmark' for the left gauge.

Turn down the pressure, connect to cylinder(has to be at TDC), adjust 'left' gauge to benchmark pressure, and read % of leakdown on right gauge.

[Bob Kontak]

Originally Posted by Packet82

set the incoming pressure on the leakdown tester, attach it to the spark plug hole, and then read the difference on the second gauge. The difference will give you your % lost.

+1

I have the mighty HF leak down tester. If I remember, setting the right hand side to zero requires some patience, as the adjustment mechanism/valve is one of the places they surely cheaped-out on to sell the thing for sub $50 - aside from the 25 cents per hour labor to build.

yelcab must not have the HF tester as his procedure makes too much sense. :-) I do recall the HF left hand gauge reading about 15-ish pounds when the right gauge is close to zero.

kevin-ct - Yes it can turn. Hold the pulley/crankshaft bolt with a wrench or socket

[rattlsnak]

I have the HF one also, and it doesn't work as 'designed' either. I did as stated above, just set the gauge and compare all the results.

[Packet82]

Originally Posted by kevin-ct

Is the engine turn a bit when you connect the air supply hose? In the pass when doing a leak down test the engine would turn a bit knocking it off TDC.

It's more likely that this will happen if you're not exactly on TDC for that cylinder, but can happen occasionally depending on the engine. Put a socket & ratchet on the fan belt pulley and wedge it slightly against the engine tin to provide some resistance. That should provide enough force to stop the engine from turning over. Also, only take out one spark plug at a time. With all the plugs out, it's easier to turn the engine over.

[yelcab1]

Originally Posted by Bob Kontak

+1
yelcab must not have the HF tester as his procedure makes too much sense. :-) I do recall the HF left hand gauge reading about 15-ish pounds when the right gauge is close to zero.

No, I don't have the Harbor Fright one. I have the expensive one that goes way past 100 psi. I do read a baseline leakage (after the input is connected but before the output is connected) and it is about 2% leakage. That means the system iteself has 2% leakage and you should subtract that from your results.

Yes, applying 100psi to the well lubed cylinders will make the piston move. You should have another person try to hold the engine pulley with a wrench and move it back and forth until you see the highest number.

[inaminit]

Since the instructions that come with the HF tool are incomplete, has anyone developed a modified proceedure for using the HF tool that gives consistent percent readings for each cylinder? Thanks for your answer.

[Scrappy]

I set the air supply regulator to 100 psig.

I connect the tester to the air supply and 0 the %guage. The other gauge reads about 10 psig.

I then connect the tester to the hose in the cylinder and read the leakdown.

Before I disconnect the tester from the cylinder line, I back off the tester regulator otherwise it will ruin the % gauge (I won't explain how I know).

Harbor Freight Forever ............

[Jcslocum]

So you are working with only 10PSI max pressure in the cylinder being tested?? I have never seen this tool and the picture isn't clear enough for me to make out the gauge on the left. If this is this is true that you are working at 10PSI, RUN to the trash can and drop this POS in and get a good tool, like this: